While Ext4 was originally merged in 2.6.19, it was marked as a development filesystem. It has been a long time coming but as planned, Ext4dev has been renamed to Ext4 in 2.6.28 to indicate its level of maturity and paving the way for production level deployments. Ext4 filesystem developer Ted Tso also endorsed Btrfs as a multi-vendor, next generation filesystem and along with the interest from Andrew Morton, Btrfs is planned to be merged before 2.6.29 is released. It will follow a similar development process to Ext4 and be initially marked as development only.

Currently F8 x86_64, though if I had it all to do over I would have stuck with CentOS. Fedora was pretty rough for the first couple of months we ran it but things have stabilized nicely.

8 GB of memory. I target about 128M per desktop user. 64 bit costs some memory up front, but has more sane memory management. I was running something like 50 desktops on 4GB on x86_32 CentOS 5, but sometimes zone_normal was touch and go. I had to reserve a lot of memory for it which cut into the buffer and page caches a bit. (Linux does a wonderful job with shared memory. Single user desktop admins don't get to see all the wonders it can perform.)

BTW, the it's a dual Xeon 3.2 GHz box. And the processor usage is only moderate. (That's why I chuckle a bit when I hear people talk as if they think multicore is likely to benefit the average user. My 60 desktop users don't even keep 2 cores overly busy!)

With x86_64, no, I don't feel any great need to for more servers. I don't have the luxury, for one thing. And more servers means more administrative overhead. That's one reason that virtualization is such a buzz word today.